Copper Peroxide Nanodots Encapsulated in a Metal-Organic Framework for Self-Supplying Hydrogen Peroxide and Signal Amplification of the Dual-Mode Immunoassay

The necessary step of directly adding hydrogen peroxide (H₂O₂) into the detection system in traditional immunoassays hampers their applications as a portable device for point-of-care analysis due to the unstable liquid form of H₂O₂. Herein, a strategy of self-supplying H₂O₂ and signal amplification triggering by copper peroxide nanodots encapsulated (CPNs) in metal-organic frameworks (ZIF-8) was proposed in an immunoassay for dual-signal detection of bisphenol A (a typical emerging organic pollutant), which was further fabricated as a lab-in-a-tube device integrated with a smartphone sensing platform. Herein, CPNs@ZIF-8 was modified on the antibody against bisphenol A; after the competitive binding of analytes, coating antigens, and antibodies, the released H₂O₂ and Cu²⁺ from encapsulated CPNs under the acidic condition will trigger a Fenton-like reaction to generate ·OH for oxidization of TMB; meanwhile, Cu²⁺ could quench the fluorescence of GSH-Au NCs, resulting in dual-mode signals for measurements. Most importantly, self-supplying H₂O₂ with high stability was undertaken by CPNs, and the remarkably increased signal molecule (CPN) loading was ascribed to the excellent capacity of metal-organic frameworks (ZIF-8). In addition, good recoveries were obtained from a colorimetric/fluorescent dual-mode strategy. The constructed device demonstrated great potential as a universal platform for rapid detection of various environmental contaminants using corresponding antibodies relying on its performance of satisfactory stability, sensitivity, and accuracy.